This invention relates to a color masterbatch resin composition for a packaging material for a photographic photosensitive material, production. thereof, a packaging material for a photographic photosensitive material formed of a color masterbatch resin composition, and production thereof.
As the a packaging material for a photographic photosensitive material, there are a resin composition composed of 30 to 95 wt. % of EEA resin containing 7 wt. % or more of EA and 5 to 70 wt. % of carbon black (EP A 0 277598), and a resin composition composed of 5 to 90 wt. % of a modified polyolefin resin, 5 to 70 wt. % of carbon black having an oil absorption value of 50 ml/100 g or more and volatile components of 3.5 % or less, and 0 to 10 wt. % of a fatty acid and/or a fatty acid metal salt (U.S. Pat. No. 5,262,471).
However, the above-mentioned conventional color masterbatch resin compositions are inferior in dispersibility of color materials including most light-shielding materials, and great agglomerates (lumps) of color material occasionally deposit on the surface of molded packaging materials for a photographic photosensitive material. The lumps cause adverse affects, such as fog with time, abnormal sensitivity, abrasion, pressure marks and fog by abrasion, upon photographic photosensitive materials packaged, and uniform coloring is difficult due to the inferior dispersibility. The deposition of lumps of color material degrades appearance of the packaging material.
In a color masterbatch process, frequency of contacts between a masterbatch resin composition and a thermoplastic resin for dilution not containing a light-shielding material is not so many. Therefore, when a color masterbatch resin composition is diluted at a high ratio, e.g. 7 times or more, by using a low grade kneading molding machine, the dispersion of a light-shielding material becomes insufficient. As a result, various troubles occur, such as uneven coloring of molded articles, jetting troubles around gates, generation of microgrits and weldlines to degrade appearance of packaging materials, delamination, decrease of physical strength or the like.